Okla. Stat. tit. 69, § 69-1512: Total expenditure limitation for fiscal year

No obligation shall be incurred by the Department of

Transportation against the State Highway Construction and

Maintenance Fund during any fiscal year in excess of the total

amount of monies accruing to said fund during such fiscal year.

Construction contracts and purchase orders issued by the Department

of Transportation, setting forth the actual or estimated cost of

construction as consideration for the cost of work to be done or

services, supplies and equipment to be furnished, shall constitute

obligations within the meaning of this act. Monthly, bimonthly or

weekly payrolls of the Department of Transportation shall constitute

current charges and shall become obligations against the State

Highway Construction and Maintenance Fund at the time the payrolls

are filed with the Director of the Office of Management and

Enterprise Services for payment.